(1) Field of the Invention
The present invention pertains to a conveyor system comprising at least one upstream or infeed conveyor that conveys objects to a pair of downstream conveyors. More specifically, the conveyor system includes a diverter positioned between the upstream conveyor and first and second downstream conveyors that splits or switches a procession of objects conveyed by the upstream conveyor to one of the two downstream conveyors. The upstream or infeed conveyor includes improvements that enable it to monitor the number of objects being conveyed by the conveyor to the diverter and to monitor any spacings occurring between the number of objects to ensure that a predetermined number of objects will remain on the conveyor before the diverter when the gates of the diverter are closed where the number of objects accumulated on the conveyor when the gates are closed will act as a cushion for additional objects being conveyed on the upstream conveyor to impact with and prevent those additional objects from falling over. In addition, the upstream conveyor includes improvements that avoid the falling over of objects as the gate of the diverter is opened to direct a procession of objects held back by the diverter gate to one of the first and second downstream conveyors.
(2) Description of the Related Art
A typical split path conveyor system employs at least one upstream or infeed conveyor and at least two downstream conveyor lanes with a diverter positioned between the upstream conveyor and the downstream conveyor lanes. The diverter selectively directs a procession of objects conveyed by the upstream conveyor to one of the two downstream conveyor lanes. Split path conveyor systems of this type are typically used in conveyor systems that load a plurality of objects onto a-rectangular pallet. The conveyor system will employ an upstream conveyor that supplies a procession of objects to the two lanes of the downstream conveyor through a diverter that directs the objects to one of the two lanes of the downstream conveyor, and then could also employ two additional pairs of further downstream conveyor lanes that are supplied with the procession of objects from the pair of downstream conveyor lanes by a pair of diverters. The number of times the path of conveyed objects is split is usually determined by the number of rows of objects that are ultimately directed to the pallet being loaded with the objects. For example, if the pallet is loaded with four rows of objects, then the upstream conveyor will be split through a diverter to a pair of downstream conveyor lanes, and then each of the downstream conveyor lanes of the pair will be split by an additional pair of diverters to two pairs of further downstream conveyor lanes, resulting in four conveyor lanes conveying four rows of objects to the pallet being loaded.
In a belt conveyor slit path conveying system, the upstream conveyor typically comprises a belt conveyor that conveys objects in upright orientations in single file between pairs of guide rails that are positioned above the belt conveyor and extend the length of the belt conveyor. The upstream conveyor conveys the procession of objects between the guide rails to a diverter that selectively directs the procession of objects received from the upstream conveyor to one of at least two downstream conveyor lanes. Like the upstream conveyors, the downstream conveyor lanes, for example a first and second downstream conveyor lane, will continue to convey the objects in their upright orientations between a pair of guide rails positioned above a conveyor belt and extending along the length of the conveyor belt. In prior art split path belt conveyors, the pair of downstream conveyor lanes defined by the pair of guide rails would include side-by-side belts driven by the same motive source at the same speed, or would include a single wide belt that would have the two pairs of guide rails defining the two downstream conveyor lanes positioned above the single wider belt. This same wider belt would convey the objects delivered from the diverter down the lengths of both of the first and second downstream conveyor lanes depending upon which of the two pairs of guide rails the diverter directed the procession of objects to from the upstream conveyor.
In split path conveying systems comprising an upstream conveyor supplying a procession of objects to at least two downstream conveyor lanes through a diverter, each of the downstream conveyor lanes would typically employ some type of sensor along its length that would communicate with the diverter and control the operation of the diverter to direct the procession of objects conveyed by the upstream conveyor to one of the downstream conveyor lanes. For example, in a split path conveyor having first and second downstream conveyor lanes, a low sensor, either a mechanical sensor or an electric sensor, would be positioned toward the outlet end of each of the first and second downstream conveyor lanes of the pair to sense the presence or absence of objects on each of the first and second downstream conveyor lanes toward their outlet ends. In addition, each downstream conveyor lane would have a full sensor adjacent its inlet end and a midway sensor positioned along the length of the conveyor between its low sensor and full sensor. These three sensors positioned along each of the downstream conveyor lanes would give some indication as to the number of objects accumulated on each of the conveyor lanes that were available to be conveyed further down the conveyor system. The sensors would also provide signals to a central processing unit CPU of the conveyor system that would control the operation of the diverter to replenish or accumulate additional objects on each of the downstream conveyor lanes in response to signals of the sensors. When the low sensor of the first downstream conveyor lane would sense the absence of conveyed objects on the first downstream conveyor lane indicating a low number of conveyed objects accumulated -in the first downstream conveyor lane, it would send a signal to the CPU that in turn would control the diverter causing the diverter to switch to direct objects conveyed by the upstream conveyor to the first downstream conveyor lane and then causing the gates of the diverter holding back objects on the upstream conveyor to open. The diverter would include a sensor that would count objects conveyed through the diverter and the gate of the diverter would remain open until a number of objects was counted that would fill the space between the low sensor and the diverter. In a like manner, when the midway sensor or the full sensor of the first downstream conveyor lane would sense the absence of conveyed objects in the first downstream conveyor lane adjacent the sensor, it would send a signal to the CPU that would again control the diverter to direct a number of bottles to the first conveyor lane to fill the space between the midway sensor or the full sensor and the diverter, depending on which sensor signals were received by the CPU. After each cycle of the upstream conveyor supplying a number of bottles to either the first or second downstream conveyor lanes, the sensors and the CPU would then control the diverter to direct bottles to the downstream conveyor lane having the fewest accumulated bottles.
In conveyor systems of the type describe above, the efficiency of the conveyor system is dependent on the speed in which it conveys objects through the conveyor system. In a split path conveyor system of the type described above, the switching of the diverter between the first and second downstream conveyor lanes would detract from the efficiency of the conveyor system. In the switching of the diverter the gate of the diverter is first closed holding back objects on the upstream conveyor as the diverter switches from the first to the second downstream conveyor lane or from the second to the first downstream conveyor lane. When the switching operation is near completion the gates of the diverter are opened allowing objects on the upstream conveyor to be directed to either one of the first and second downstream conveyor lanes. Each time the diverter switches between the first and second conveyor lanes, the procession of objects being conveyed by the conveying system is stopped. Although the conveyance of objects is stopped for only a short period of time, multiplied by the number of times the diverter would switch between the first and second downstream conveyor lanes the time period that the procession of objects conveyed by the conveyor system is stopped due to the switching of the diverter becomes significant.
To make up for the lost time due to the switching operation of the diverter, increasing the speeds of the upstream conveyor and the first and second downstream conveyor lanes was considered for split path conveyor systems. However, in conveyor systems conveying lightweight objects, for example belt conveyor systems conveying empty blow-molded plastic bottles, the efficiency of the system could not be increased by simply increasing the speed of the conveyor belts. As bottles conveyed on one of the conveyor belts would come into contact with bottles accumulated at the outlet end of the same belt, the increased speed of the conveyor would cause the conveyed bottles to impact with the accumulated bottles with such a force that one or more of the conveyed bottles would be knocked backward from their upright orientations as a result of the impact. Therefore, to prevent the lightweight objects, for example blow-molded bottles, from falling over on impact along the conveyor system, the overall speed of the conveyor belts is limited and cannot be increased above the acceptable impact speed.
Controlling the speeds of the upstream conveyor and the conveyor of the first and second downstream conveyor lanes in split path conveyor systems was also considered to increase their efficiency. It was thought that the speed of the upstream conveyor and the speed of one of the first and second downstream conveyor lanes to which the diverter was directing bottles could be increased after the gate of the diverter-was opened and then gradually decreased before the bottles provided by the upstream conveyor to the downstream conveyor would impact with bottles already accumulated on the particular downstream conveyor lane. The gate of the diverter would then be closed and the diverter would be switched to the other downstream conveyor lane, the gates opened and the speeds increased to quickly supply bottles from the upstream conveyor to the other downstream conveyor lane. However, because both the first and second downstream conveyor lanes extended over one wide conveyor belt or two side-by-side belts driven by the same motive source, increasing the speed of one lane of the downstream conveyor to quickly supply it with a number of bottles from the upstream conveyor would also result in increasing the speed of the other lane of the downstream conveyor. This would result in uncontrollable bottle impact situations. For example, increasing the speed of the upstream conveyor and the first downstream conveyor lane to provide the first downstream conveyor lane with a sufficient number of bottles to fill the space between its low sensor and the diverter would also result in increasing the speed of the second conveyor lane. If a supply of bottles had been previously directed to the second conveyor lane by the diverter to fill the space between the midway sensor of the second conveyor and the diverter, the increased speed of the first downstream conveyor lane would also increase the speed of the second downstream conveyor lane causing the supply of bottles provided to the second downstream conveyor lane to impact with the bottles already accumulated on the second downstream conveyor lane at the increased speed. As a result, controlling the speeds of the downstream conveyor increasing its speed to quickly supply bottles to a conveyor lane and then decreasing the speed before the bottles supplied to the one particular conveyor lane impacted with bottles accumulated on the one particular conveyor lane was not seen as a solution to increasing the time efficiency of split path conveyor systems.
In increasing the speed at which processions of bottles were conveyed from the upstream conveyor through the diverter to one of the downstream conveyors, it was observed that when the gates of the diverter were closed to switch the diverter between the downstream conveyors, if only one or a small number of bottles conveyed by the upstream conveyor would impact with the closed gates some of the bottles would likely fall over. However, if the diverter gates were closed when a number of bottles were accumulated on the conveyor behind the diverter gates, the impact of additional bottles conveyed by the upstream conveyor with the accumulated number of bottles would cushion the impact and reduce the likelihood of bottles falling over. However, when the conveyor system is operated at increased speeds it is not always possible to maintain an accumulation of bottles on the upstream or infeed conveyor behind the diverter gates when the gates are closed to insure that individual bottles or small groups of bottles would not impact with the closed gates and possibly fall over.
In addition, as speeds are increased the force exerted by an accumulation of objects on a diverter gate holding back the objects on the surface of the moving conveyor would increase. This force could increase to the point where when the gate of the diverter is opened to direct the accumulated procession of objects down one of the downstream conveyors the opening of the gate could cause the lead object or objects to spring out of the gate and fall over in the conveyor path before the procession of objects. This potential for objects falling over is further increased where the conveyor section includes a vacuum for holding objects down on the conveyor surface. The addition of vacuum further increases the pressure created in the held back procession of objects behind the diverter gate.
What is needed to overcome the deficiencies in split path conveyor systems is an arrangement of sensors on the systems that provide a more accurate indication of the extent of accumulated conveyed objects on each of the downstream conveyors supplied by the upstream conveyor, and separate downstream conveyors with adjustable speed drive systems that are controlled by the CPU of the downstream conveyors to increase the speeds of the downstream conveyors in certain sensed conditions to quickly accumulate conveyed objects on the downstream conveyors and then decrease the speeds of the downstream conveyors to avoid a level of impact of conveyed objects with accumulated objects on the downstream conveyors that would cause some of the conveyed objects to be knocked over from their upright positions due to the impact.
Also what is needed to overcome the deficiencies in split path conveyor systems is a mechanism by which the gaps that appear between objects conveyed in a procession by the upstream conveyor to one of the two downstream conveyors can be monitored to insure that the occurrence of gaps between conveyed objects does not amount to a level where there is an insufficient number of objects or bottles conveyed by the upstream conveyor to act as a cushion when the gates of the diverter are closed to cushion the impact of gapped accumulated bottles traveling toward the gate and later arriving objects or bottles with the objects accumulated on the upstream conveyor behind the closed diverter gates. In addition, relieving the pressure of accumulated objects held behind the closed gates of the diverter just prior to the gates being opened would avoid the problem of one or more objects being propelled through the gates and potentially falling over in the conveyor path as the gates are opened.
The conveyor system of the invention in the illustrative embodiment to be described supplies four lanes of conveyed objects to a palletizer. However, the features of the conveyor system of the invention could be employed in supplying more than four lanes or fewer than four lanes of conveyed objects, and the conveyor system has applications other than supplying rows or lanes of objects to a palletizer. It should be understood that the description of the conveyor system of the invention as ultimately including four lanes of conveyed objects that are supplied to a palletizer is illustrative only and is not intended to limit the claimed features of the invention. Also, in the illustrative embodiment of the conveyor system, the conveyors are belt-type conveyors that convey empty plastic blow-molded bottles. However, the inventive features of the conveyor system could be employed in other types of conveyor systems, for example air conveyor systems, and may also be employed on conveyor systems in conveying other types of objects.
The illustrative embodiment of the conveyor system of the invention employs a single upstream or infeed conveyor, a pair of intermediate conveyors, and two pairs of downstream conveyors. Each of the conveyors is a belt type conveyor, for example a belt conveyor manufactured by Ouellette Machinery Systems, Inc. of Fenton, Mo. that employs a Rexnord(copyright) table top chain conveyor belt. Each of these conveyors have continuously running belts as the conveyor system is operated and have guide rails on opposite sides of the belts that direct the procession of bottles in single file along each of the conveyors. The bottles are conveyed in upright orientations of the bottles on the belts and the belt top surfaces are sufficiently smooth to enable the top surfaces to slide beneath the conveyed bottles when the procession of conveyed bottles is held back by a gate of the conveyor system allowing bottles to accumulate on the conveyor.
Each of the conveyors of the conveyor system is driven by a motive system, for example an electric motor and a speed shiftable power transmission system or an electric motor that can be controlled to vary its speeds, that is operable to run the conveyor at a plurality of different speeds and preferably at least a fast and a slow speed. The motive system of each conveyor can adjust the speed of the conveyor belt independently of the other conveyors.
The illustrative embodiment of the conveyor system employs three diverter assemblies with a first diverter assembly positioned between the upstream or infeed conveyor and the pair of intermediate conveyors and a pair of downstream diverter assemblies, second and third diverter assemblies, positioned between the pair of intermediate conveyors and the two pairs of downstream conveyors. In the preferred embodiment the diverter assemblies are diverter models BD250-2 or BD350-2 manufactured by Ouellette Machinery Systems, Inc. of Fenton, Mo. The diverters function like railroad track switches directing a procession of bottles supplied by one conveyor to the diverter to one of the two conveyors at the opposite side of the diverter. For example, the diverter between the upstream conveyor and the pair of downstream conveyors will selectively direct a procession of bottles conveyed by the upstream conveyor to one of the pair of downstream conveyors. The diverter has a pair of spaced, vertical panels that are switchable between the pair of intermediate conveyors so that the diverter may direct the procession of bottles conveyed by the upstream conveyor to either one of the pair of intermediate conveyors depending on sensed conditions of bottles accumulated on the pair of intermediate conveyors. The diverter also has a pair of gates, one mounted on each panel. The gates are operable between closed and open positions. In the closed positions they extend across the conveyor path and hold back bottles conveyed by the particular conveyor, allowing a number of bottles to accumulate on the conveyor behind the gate. In the opened positions they allow bottles to be conveyed past the gates. Each of the diverters is also provided with a sensor, either mechanical or electrical and preferably a photo sensor, that is mounted on the panels and communicates with a central processing unit (CPU) of the system to count the number of bottles conveyed through the diverter. The CPU uses this information in controlling the opening and closing of the gates of the diverter assembly.
In the preferred embodiment of the conveyor system each of the pair of intermediate conveyors and each of the two pairs of downstream conveyors have a plurality of sensors positioned along the lengths of the conveyors between their inlet and outlet ends. Preferably, at least two sensors are positioned along the lengths of each of the conveyors. In the illustrative example three sensors are used with a low sensor positioned adjacent the outlet end of the conveyor, a full sensor positioned adjacent the inlet end of the conveyor and a midway sensor positioned along the conveyor between the low sensor and full sensor. Preferably, the sensors employed are photo sensors that are capable of detecting the presence or absence of a bottle on the conveyor at the location of the sensor. In addition, the midway sensor of each conveyor is preferably positioned slightly toward the low sensor of each conveyor so that there is a greater distance between the midway sensor and the full sensor than between the midway sensor and the low sensor. The sensors of the conveyors communicate through a central processing unit (CPU) with the motive sources of the conveyors to control the changing of speeds of the individual conveyors depending on conditions sensed by the sensors along the lengths of the conveyors. In addition, the sensors of each conveyor communicate through the CPU with the diverter assemblies causing the gates of the diverter assemblies to open and close and causing the diverter panels of the diverter assemblies to switch between the conveyors supplied with bottles from the diverter assemblies depending on sensed conditions of the sensors. For example, if the sensors of a first conveyor of the pair of intermediate conveyors are all opened indicating the absence of bottles at the low sensor, the midway sensor and the full sensor, these sensors send a signal to the first diverter assembly causing the diverter panels of the diverter assembly to be switched to the first intermediate conveyor and causing the gate of the first diverter assembly to open so that a procession of bottles is directed from the upstream conveyor through the diverter assembly to the first conveyor of the pair of intermediate conveyors. The signal sent by all three of the sensors along the first intermediate conveyor indicates to the diverter assembly that the first intermediate conveyor can be supplied with a number of bottles that would fill the length of the first intermediate conveyor between the low sensor and the first diverter assembly. The counter photo sensor of the diverter assembly senses the bottles that pass by the gate and the CPU counts the bottles until a number of bottles that would fill the length of the first intermediate conveyor between the low sensor and the diverter assembly passes the gate, whereupon the diverter assembly will close the gate and switch the diverter panels to the second intermediate conveyor to supply bottles to the second intermediate conveyor as needed. After each cycle of the upstream conveyor supplying a number of bottles to either the first or second downstream conveyors, the sensors and the CPU would then control the diverter to direct bottles to the downstream conveyor having the fewest accumulated bottles. If the low sensor of the first intermediate conveyor senses the presence of bottles on the conveyor and the midway sensor and full sensor do not sense the presence of bottles, the sensors cause signals to be sent to the diverter assembly causing it to switch the diverter panels to direct bottles from the upstream conveyor to the first intermediate conveyor. The sensors also send signals to the diverter assembly causing the diverter assembly to open its gate and allow a number of bottles to pass through the gate that is sufficient to fill the space between the midway sensor and the first diverter assembly. With this number of bottles counted by the sensor of the diverter assembly, the gate is controlled to close and the diverter panels are switched to the second intermediate conveyor to supply bottles to that conveyor as needed. In addition, if while the gate is opened and the upstream conveyor is supplying a number of bottles to the first intermediate conveyor that will fill the space between the midway sensor and the full sensor and the low sensor opens indicating that the last of the bottles accumulated on the intermediate conveyor has passed the low sensor, the low sensor sends a signal to the CPU and the CPU counter counting bottles that pass the counter photo sensor will change from counting a number of bottles that will fill the space between the midway sensor and the diverter assembly to counting a number of bottles that will fill the space between the low sensor and the diverter assembly and then close the gate when this number of bottles has passed by the diverter sensor. By converting the number of bottles being counted by the CPU as the bottles are being counted the conveyor system saves time.
In addition, the conditions sensed by the low sensor, the midway sensor and the full sensor also control the speeds of each of the conveyors. For example, if each of the three sensors along the first intermediate conveyor sensed an open condition or the absence of bottles along the three sensor positions of the conveyor, the sensors would send a signal to the CPU that would then control the motive sources of the upstream conveyor and the first intermediate conveyor causing them to operate at slow speeds as the gate of the first diverter directing bottles to the first intermediate conveyor is opened and then to ramp up to high speeds to quickly supply the bottles from the upstream conveyor through the diverter to the first intermediate conveyor. When the counter sensor of the diverter determines that there are only a few bottles left to fill the space between the low sensor and the diverter, then the CPU controls the motive sources of the upstream conveyor and the motive source of the first intermediate conveyor to ramp down to slow speeds at which the gate was opened. This reduces the impact force of the conveyed bottles on the first intermediate conveyor with any accumulated bottles on the first intermediate conveyor that are downstream of the low sensor and thus avoids a level of impact of the bottles that would cause bottles at the end of the stream of conveyed bottles on the first intermediate conveyor from falling over. In a like manner, if the low sensor of the first intermediate conveyor senses the presence of bottles but the midway sensor and full sensor do not sense the presence of bottles, then the gate is opened to supply a number of bottles to the first intermediate conveyor that will fill the space between the midway sensor and diverter and the speed of the upstream conveyor and the speed of the first intermediate conveyor are controlled to increase from the low speed at the time the gate is opened to the high speed. The upstream conveyor and first intermediate conveyor are maintained at high speeds until the counter photo sensor at the diverter and the CPU detect that only a few bottles are left in the number of bottles supplied to the first intermediate conveyor at which point the speeds of the upstream conveyor and first intermediate conveyor are reduced to slow speeds to minimize the impact of the bottles conveyed to the first intermediate conveyor with the bottles already accumulated on the first intermediate conveyor and the slower moving bottles also enable the gates to close between the last bottle counted and the first bottle to be held. In this manner, bottles are quickly conveyed along each of the conveyors at high speed, but then the speed of conveyance is reduced to avoid the problem of impacting of bottles at high speeds causing the bottles at the end of a conveyed number of bottles from falling over.
Each of the pair of intermediate conveyors of the conveying system and the two pairs of downstream conveyors of the conveying system have at least two but preferably three photo sensors positioned along their lengths that emit signals that communicate with the CPU which controls the gates and the panels of the diverters that direct bottles to the conveyors and also controls the motive sources of each of the conveyors and the photo counters of each of the diverter assemblies as described above.
The upstream or infeed conveyor is also provided with sensors that sense gaps between adjacent bottles being conveyed by the infeed conveyor to the intermediate or downstream conveyors. This information is communicated to the CPU and the gaps for a number of bottles being conveyed by the upstream conveyor to the downstream conveyors is summed. The sum of the gaps is compared to an acceptable predetermined gap size for the number of bottles being conveyed to the downstream conveyors to insure that the summed gap does not become too large as to present the potential problem of too few bottles being accumulated before the first diverter gates to act as a cushion when the gates are closed. If the predetermined total gap is reached by the gaps sensed by the sensor and summed by the CPU the upstream conveyor will continue to operate at a reduced speed while an additional set number of bottles is conveyed past the sensor. If the gap count does not correct itself as the set number of bottles is conveyed past the sensor the CPU will control the upstream conveyor to close the gates of the first diverter to avoid the potential problem of too few bottles accumulated behind the gates to cushion the bottles traveling toward the gate and later arriving bottles impacting with each other on the conveyor and potentially falling over. With the gates closed the procession of bottles are again allowed to accumulate on the upstream conveyor for a predetermined time period, following which the gates are opened.
In order to insure that an accurate measurement is made of the gaps between bottles and the total summed gaps that pass by the sensor, the upstream conveyor employs a unique sensor arrangement of a first sender and receptor pair and a second sender and receptor pair that are positioned side by side on opposite sides of the conveyor to obtain an accurate gap count.
In addition, to avoid the problem of the pressure build up in a procession of bottles accumulated on the upstream conveyor and held back by the first diverter gate potentially projecting one or more bottles outwardly from the diverter gate as the gate is opened, the opening of the diverter gate is timed so that the upstream conveyor is allowed to decrease in speed just prior to the opening of the first diverter_gate, thereby reducing the pressure among the bottles accumulated behind the first diverter gate on the upstream conveyor. Furthermore, when a vacuum system is employed with the upstream conveyor to assist in holding down conveyed bottles on the top surface of the conveyor, the vacuum created by the vacuum system drawing bottles down onto the upstream conveyor will decrease a short time before the opening of the first diverter gate to further reduce the pressure built up among bottles accumulated behind the first diverter gate and thereby avoid the problem of one or two bottles projecting forwardly through the gate as the gate is opened and potentially falling over.
The split path conveying system of the invention constructed in the manner described above significantly increases the time efficiency of the split path conveyor system over those of the prior art.